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■ The Novel Formation of a Dibenzocyclohepta[b]pyridine by an Abnormal Hofmann Degradation of a Diphenolic Tetrahydroprotoberberinium Salt

Tetsuji Kametani,* Makoto Takemura, Keiichi Takahashi, Mitsuhiro Takeshita, Masataka Ihara, and Keiichiro Fukumoto

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan

Abstract

Heating coreximine methiodide (5) with methanolic potassium hydroxide gave the secoprotoberberine (14) and 5,5a,6,7,8-pentahydro-3,11-dihydroxy-2,10-dimethoxybenz[b,e]-4H-azuleno[3,2,1-ij]isoquinoline (15), but not the methine base (10) usually formed by Hofmann degradation. The possible biogenesis of these two abnormal Hofmann degradation products from protoberberine alkaloids is discussed.